title: Enhanced Heavy Metal Tolerance in Two Strains of Photosynthetic Euglena gracilis by Preexposure to Mercury or Cadmium
abstract: The effects of different concentrations of Hg, Cd, and Pb on cell growth, oxygen consumption, and production and contents of chlorophyll a and b of Z and B strains of Euglena gracilis was studied. Cell uptake of Cd and Pb was also determined. A greater cell density reached in the presence of Cd2+ correlated with a lower metal uptake capacity in B-strain cells. Cells of Z strain, preexposed to low concentrations of either Hg2+ (1.5 μM) or Cd2+ (50 μM) for several generations showed improved heavy metal tolerance (greater cell density and viability) together with similar metal uptake capacity. Because Cd2+ preadaptation but not Hg2+ pretreatment induced a significant increase in the content of acid-soluble thiols, the data suggest the existence of different mechanisms of heavy metal detoxification in Euglena. The fact that Z-strain cells showed a greater Cd2+ uptake under all the conditions assayed suggests that Z strain would be more suitable for bioremediation of polluted waters.
authors.affiliation: Departamento de Bioquimica, Instituto Nacional de Cardiologia, Mexico, D.F. 14080
authors.initials: S
authors.lastname: Devars
authors.initials: R
authors.lastname: Hernandez
authors.initials: R
authors.lastname: Moreno-Sanchez